When the smile is a cue to familiarity.

The question discussed in the two following experiments concerns the effect of facial expressions on face recognition. Famous and unknown faces with neutral or smiling expression were presented for different inspection durations (15 ms vs 1000 ms). Subjects had to categorize these faces as famous or unknown (Experiment 1), or estimate their degree of familiarity on a rating scale (Experiment 2). Results showed that the smile increased ratings of familiarity for unfamiliar faces (Experiments 1 and 2) and for famous faces (Experiment 2). These data are discussed in the framework of current face-recognition models and are interpreted in terms of social value of the smile. It is proposed that the smiling bias found here acts at the level of the decision process.